At the time of infusion into a patient or in other similar situations, an indwelling needle assembly connected to an infusion line is used to puncture a patient's blood vessel and is left placed there.
Such an indwelling needle assembly includes a hollow outer needle, an outer needle hub firmly attached to the proximal end of the outer needle, an inner needle having a sharp needle point at the distal end thereof and inserted in the outer needle, and an inner needle hub firmly attached to the proximal end of the inner needle. An example is disclosed in Japanese Application Publication No. 2002-263197. In addition, in the outer needle hub are contained a valve element (stanching valve), and an operation member (pusher) which operates the opening and closing of the valve element.
At the time of puncturing a patient's blood vessel by the indwelling needle assembly, the puncturing operation is conducted in an assembled state (see FIG. 1 of the above-cited Japanese application publication) in which the inner needle is inserted in the outer needle and the needle point of the inner needle is protruded from the distal end of the outer needle. Then, when the needle point of the inner needle reaches the inside of the blood vessel, blood having flowed in through an opening at the needle point flows through the inner cavity of the inner needle into the inside of the transparent inner needle hub (flashback). This makes it possible to confirm (visually check) the fact that the inner needle has arrived in the blood vessel. When this flashback is confirmed, the outer needle is advanced, and the outer needle is inserted in the blood vessel.
Next, while gripping the outer needle by hand, the inner needle is drawn out of the outer needle (see FIG. 2 of the above-cited Japanese application publication). As a result, placement of the outer needle in the blood vessel can be achieved. Besides, in this instance, the valve element in the outer needle hub is in a closed state, so that leakage of blood is prevented.
Subsequently, a tubular connector (tube) is connected to a proximal portion of the outer needle hub (see FIG. 3 of the above-cited Japanese application publication). By the connector thus connected, the operation member inside the outer needle hub is pushed in the distal direction, to push open the valve element. Consequently, the valve element is put into an open state, so that an infusion liquid can be administered from the connector side to the outer needle side.
Meanwhile, the operation member pressed by the connector is set in a state in which its distal portion is protruded to the distal side relative to the valve element (see FIG. 3 of the above-cited Japanese application publication). When the infusion liquid is administered in this state, a part surrounded by a wall portion defining a flow path and an outer circumferential portion of a distal portion of the operation member that is protruding from the valve element becomes a dead angle, so that the infusion liquid cannot go around into the part. Accordingly, blood is left stagnating in the part. Thus, there has been a problem that the stagnating blood becomes a source of bacterial proliferation or a source of thrombus.